window.onload = () => {
  setInterval(()=> {
    const show = document.querySelector('span[data-show]');
    const next = show.nextElementSibling || document.querySelector('span:first-child');
    const up = document.querySelector('span[data-up]');
      
    if(up) {up.removeAttribute('data-up');}
    show.removeAttribute('data-show');
    show.setAttribute('data-up', '');
    next.setAttribute('data-show', '');
  }, 2000);
}
